Synthesis and in vitro antitumor activity of ring C and D-substituted phenanthrolin-7-one derivatives, analogues of the marine pyridoacridine alkaloids ascididemin and meridine

A series of cycle C and D-substituted phenanthrolin-7-ones, analogues of the marine pyridoacridines meridine and ascididemin have been synthesized on the basis of Diels-Alder reactions involving quinoline-5,8-dione and 2- (or un)-substituted-N,N-dimethylhydrazones. All the compounds were evaluated for in vitro cytotoxic activity against 12 distinct human cancer cell lines. They all exhibit cytotoxic activity with IC(50) values at least of micromolar order.     

Studies on the Biosynthesis of the ergosterol side chain

1. A convenient synthesis of 24-methylene[23,25-(3)H(3)]dihydrolanosterol is described. 2. A general anaerobic-aerobic method for the incorporation of sterols into whole yeast cells is also described and illustrated by experiments with (3)H-labelled lanosterol. 3. The method was used to convert labelled 24-methylene-dihydrolanosterol into ergosterol, in good yield, by Saccharomyces cerevisiae. 4. Degradation of the biosynthetic ergosterol provided confirmation of the conversion, which supports the proposed mechanism for the biosynthesis of the ergosterol side chain. 5. Mechanisms for the further conversion of the 24-methylene side chain into the ergosterol side chain are discussed and it was shown that a compound, [3alpha-(3)H(1)]-ergost-7-en-3beta-ol, with a fully saturated side chain, can also be efficiently incorporated into ergosterol. 6. This result was confirmed by a procedure involving formation of the 5,8-epidioxide and subsequently the 5,8-epidioxy-22,23-epoxide of the biosynthetic ergosterol.     

Analogues of Azepinomycin as Inhibitors of Guanase

Abstract

Synthesis and biochemical screening against guanase of analogues of the naturally occurring guanase inhibitor azepinomycin (2) are reported. Compound e-amino-5,6,7,8,-tetrahydro-4H-imidazo[4,5-e][1,4]diazepine-5,8-dione (3) was synthesized in six steps commencing with 1-benzyl-5-nitroimidazole-4-carboxylic acid (5). Compound 3 and its synthetic precursor 3-benzyl-6-(N-benzyloxycarbonyl)amino-5,6,7,8-tetrahydro-4H-imidazo[4,5-e][1,4]diazepine-5,8-dione (12) were screened against rabbit liver guanase. Both were found to be moderate inhibitors of the enzyme with K₁′s in the range of 10^?4 M.     

Synthesis of pyridino[2,3-f]indole-4,9-dione and 6,7-disubstituted quinoline-5,8-dione derivatives and evaluation on their cytotoxic activity

We report upon the synthesis of the following derivatives: N-substituted-pyridino[2,3-f]indole-4,9-dione, and 6-(alpha-diethoxycarbonyl-methyl)-7-substituted-amino-quinoline-5,8-dione, which contain the active quinoline-5,8-dione (VII) moiety. The cytotoxic activities of these compounds have been tested in SRB (SulfoRhodamine B) assays against the cancer cell lines of A-549 (human lung cancer), SK-MEL-2 (human melanoma cancer), SK-OV-3 (human ovarian cancer), XF-498 (human brain cancer) and HCT 15 (human colon cancer). The compound, N-benzyl-3-ethoxycarbonyl-2-hydroxy-pyridino[2,3-f]indole-4,9-dione (A-9), also showed higher activity than cis-platin. The highest level of cytotoxic activity in these human tumor cell lines was observed in the compound 6-(alpha-diethoxycarbonyl-methyl)-7-(2-methyl-phenylamino)-quinoline-5,8-dione (B-3).     

Three further naphthoquinones produced by Fusarium solani

Three naphthoquinone pigments are described which were produced by Fusarium solani. They are 2,3-dihydro-5,8-dihydroxy-6-methoxy-2-hydroxymethyl-3-(2-hydroxypropyl)-1,4-naphthalenedione, 2,3-dihydro-5-hydroxy-4-hydroxymethyl-8-methoxy-naphtho[1,2-b]furan-6,9-dione and 5,8-dihydroxy-2-methoxy-6-hydroxymethyl-7-(2-hydroxypropyl)-1,4-naphthalenedione. One of these pigments was shown to be the precursor of the other two.     

The Synthesis of Two Novel Ring-Expanded Xanthine Nucleosides Containing the Imidazo[4,5-e][1,4]Diazepine Ring System

Abstract

The synthesis of two regioisomeric nucleosides, 4,5,7,8-tetrahydro-6H-3-(β-D-ribofuranosyl)imidazo[4,5-e][1,4]diazepin-5,8-dione (2) and its 1-glycosyl analogue (3) is reported. They were prepared by ribosydation of the heterocyclic aglycon 4 which in turn was synthesized in three steps from 4(5)-nitroimidazole-5(4)-carboxylic acid (5). Distinction between the two isomers was achieved by an unequivocal synthesis of 2.     

Ancistrolikokine D,a 5,8'-coupled naphthylisoquinoline alkaloid,and related natural products from Ancistrocladus likoko

A new naphthylisoquinoline alkaloid, ancistrolikokine D, and the likewise 5,8'-coupled alkaloid ancistroealaine A, as well as two further, biosynthetically related, but nitrogen-free natural products, ancistronaphthoic acid B and cis-isoshinanolone, have been isolated from Ancistrocladus likoko J. LEACUTE;ONARD (Ancistrocladaceae). The 5,8'-coupling of the new alkaloids and of the alkaloids isolated earlier hints at a close phylogenetic relationship of A. likoko to other Central African Ancistrocladus species. The compounds show moderate activities against Leishmania donovani, Trypanosoma cruzi, and Trypanosoma brucei rhodesiense.     

Isolation and antimalarial activity of peroxydisulfate oxidation products of primaquine

Five compounds formed by peroxydisulfate oxidation of primaquine were isolated using chromatographic methods and evaluated for antimalarial activity in vitro. One compound 6-methoxy-5,8 bis(4′-amino-1′-methylbutylamino)quinoline [P₁] was found to have good gametocytocidal activity against Plasmodium yoelli infected mice at 10 mg kg⁻¹ dose in vivo.     

Canarion,ein neues naphthochinon aus Usnea canariensis

The structure of canarione, a new naphthoquinone from the lichens Usnea canariensis and U. hookeri was elucidated by UV, ¹H-NMR, ¹³C-NMR, mass spectrometry, and chemical degradation as 5,8-dihydroxy-2-methyl-4H-naphtho [2,3b]-pyran-4,6,9 (6H, 9H)- trione.     

Overexpression of Coptis japonica norcoclaurine 6-O-methyltransferase overcomes the rate-limiting step in Benzylisoquinoline alkaloid biosynthesis in cultured Eschscholzia californica

Benzylisoquinoline alkaloids are one of the most important secondary metabolite groups, and include the economically important analgesic morphine and the antimicrobial agent berberine. To improve the production of these alkaloids, we investigated the effect of the overexpression of putative rate-limiting step enzymes in benzylisoquinoline alkaloid biosynthesis. We introduced two O-methyltransferase [Coptis japonica norcoclaurine 6-O-methyltransferase (6OMT) and 3'-hydroxy-N-methylcoclaurine 4'-O-methyltransferase (4'OMT)] expression vectors into cultured California poppy cells to avoid the gene silencing effect of endogenous genes. We established 20 independent lines for 6OMT transformants and 15 independent lines for 4'OMT transformants. HPLC/liquid chromatography-mass spectrometry (LC-MS) analysis revealed that the overexpression of C. japonica 6OMT was associated with an average alkaloid content 7.5 times greater than that in the wild type, whereas the overexpression of C. japonica 4'OMT had only a marginal effect. Further characterization of 6OMT in California poppy cells indicated that a 6OMT-specific gene is missing and 4OMT catalyzes the 6OMT reaction with low activity in California poppy, which supports the notion that the 6OMT reaction is important for alkaloid biosynthesis in this plant species. We discuss the importance of 6OMT in benzylisoquinoline alkaloid biosynthesis and the potential for using a rate-limiting step gene to improve alkaloid production.     

2D-NMR and ATR-FTIR study of the structure of a cell-selective diastereomer of melittin and its orientation in phospholipids

Melittin, a 26 residue, non-cell-selective cytolytic peptide, is the major component of the venom of the honey bee Apis mellifera. In a previous study, a diastereomer ([D]-V(5,8),I(17),K(21)-melittin, D-amino acids at positions V(5,8),I(17),K(21)) of melittin was synthesized and its function was investigated [Oren, Z., and Shai, Y. (1997) Biochemistry 36, 1826-1835]. [D]-V(5,8),I(17),K(21)-melittin lost its cytotoxic effects on mammalian cells; however, it retained antibacterial activity. Furthermore, [D]-V(5,8),I(17),K(21)-melittin binds strongly and destabilizes only negatively charged phospholipid vesicles, in contrast to native melittin, which binds strongly also zwitterionic phospholipids. To understand the differences in the properties of melittin and its diastereomer, 2D-NMR experiments were carried out with [D]-V(5,8),I(17),K(21)-melittin, and polarized attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy experiments were done with both melittin and [D]-V(5,8), I(17),K(21)-melittin. The structure of the diastereomer was characterized by NMR in water, as well as in three different membrane-mimicking environment, 40% 2,2,2-trifluoroethanol (TFE)/water, methanol, and dodecylphosphocholine/phosphatidylglycerol (DPC/DMPG) micelles. The NMR data revealed an amphipathic alpha-helix only in the C-terminal region of the diastereomer in TFE/water and methanol solutions and in DPC/DMPG micelles. ATR-FTIR experiments revealed that melittin and [D]-V(5,8),I(17),K(21)-melittin are oriented parallel to the membrane surface. This study indicates the role of secondary structure formation in selective cytolytic activity of [D]-V(5,8), I(17),K(21)-melittin. While the N-terminal helical structure is not required for the cytolytic activity toward negatively charged membranes and bacterial cells, it appears to be a crucial structural element for binding and insertion into zwitterionic membranes and for hemolytic activity.     

Regioselective substitution of 6,7-dichloroquinoline-5,8-dione: synthesis and X-ray crystal structure of 4a,10,11-triazabenzo[3,2-a]fluorene-5,6-diones

6,7-Dichloroquinoline-5,8-dione (1) was reacted with a number of 2-aminopyridine derivatives. Of the several possible products of this reaction, 4a,10,11-triazabenzo[3,2-a]fluorene-5,6-dione (6), produced by condensation and rearrangement, was obtained as the major product, and its structure was subsequently unambigously determined by X-ray crystallographic study. Ortho-quinones were produced via nucleophilic substitution at position C7, which was unexpected, considering that para-quinones were produced via C6 substitution in the reaction between compound 1 and ethyl acetoacetate in our previous work. Such unexpected nucleophilic substitution at C7 provides an effective, yet simple route, to the preparation of biologically active ortho-quinone derivatives.     

Synthesis and antiplatelet, antiinflammatory, and antiallergic activities of substituted 3-chloro-5,8-dimethoxy-1,4-naphthoquinone and related compounds

2-Amino (6), 2-alkylamino (7–8), 2-methoxy (9), 2-acetamido (10), and 5,8-diacetoxy (11) derivatives of the lead compound 2,3-dichloro-5,8-dimethoxy-1,4-naphthoquinone (4) were synthesized, together with 6,7-dichloro-5,8-dimethoxy-1,4-naphthoquinone (5), a positional isomer of 4. Antiplatelet, antiinflammatory, and antiallergic activities were evaluated, and most compounds were quite potent in all assays. Compounds 5 and 9–11 were especially active; however, 5 was ineffective against neutrophil superoxide formation, and 10 was ineffective against mast cell degranulation.     

Effect of hydroxy substituent position on 1,4-naphthoquinone toxicity to rat hepatocytes.

The effect of hydroxy substitution on 1,4-naphthoquinone toxicity to cultured rat hepatocytes was studied. Toxicity of the quinones decreased in the series 5,8-dihydroxy-1,4-naphthoquinone greater than 5-hydroxy-1,4-naphthoquinone greater than 1,4-naphthoquinone greater than 2-hydroxy-1,4-naphthoquinone, and intracellular GSSG formation decreased in the order 5,8-dihydroxy-1,4-naphthoquinone greater than 5-hydroxy-1,4-naphthoquinone much greater than 1,4-naphthoquinone much greater than 2-hydroxy-1,4-naphthoquinone. The electrophilicity of the quinones decreased in the order 1,4-naphthoquinone much greater than 5-hydroxy-1,4-naphthoquinone greater than 5,8-dihydroxy-1,4-naphthoquinone much greater than 2-hydroxy-1,4-naphthoquinone. Treatment of the hepatocytes with BSO (buthionine sulfoximine) or BCNU (1,3-bis-2-chloroethyl-1-nitrosourea) increased 5-hydroxy-1, 4-naphthoquinone and 5,8-dihydroxy-1,4-naphthoquinone toxicity, whereas neither BSO nor BCNU largely affected 1,4-naphthoquinone and 2-hydroxy-1, 4-naphthoquinone toxicity. Dicumarol increased the toxicity of 1,4-naphthoquinone dramatically and somewhat the toxicity of 2-hydroxy-1,4- naphthoquinone, whereas 5-hydroxy-1,4-naphthoquinone and 5,8-dihydroxy-1,4-naphthoquinone toxicity increased only slightly. The toxicity of 5,8-dihydroxy-1,4-naphthoquinone decreased dramatically in reduced O2 concentration, whereas 1,4-naphthoquinone, 5-hydroxy-1,4-naphthoquinone, and 2-hydroxy-1,4-naphthoquinone toxicity was not largely affected. It was concluded that 5,8-dihydroxy-1,4-naphthoquinone toxicity is due to free radical formation, whereas the toxicity of 1,4-naphthoquinone and of 5-hydroxy-1,4-naphthoquinone also has an electrophilic addition component. The toxicity of 2-hydroxy-1,4-naphthoquinone could not be fully explained by either of these phenomena.     

Synthesis and in vitro antitumor activity of thiophene analogues of 5-chloro-5,8-dideazafolic acid and 2-methyl-2-desamino-5-chloro-5,8-dideazafolic acid

N-[5-[N-(2-Amino-5-chloro-3,4-dihydro-4-oxoquinazolin-6-yl)methylamino]-2-thenoyl]-L-glutamic acid (6) and N-[5-[N-(5-chloro-3,4-dihydro-2-methyl-4-oxoquinazolin-6-yl)methylamino]-2-thenoyl]-L-glutamic acid (7), the first reported thiophene analogues of 5-chloro-5,8-dideazafolic acid, were synthesized and tested as inhibitors of tumor cell growth in culture. 4-Chloro-5-methylisatin (10) was converted stepwise to methyl 2-amino-5-methyl-6-chlorobenzoate (22) and 2-amino-5-chloro-3,4-dihydro-6-methyl-4-oxoquinazoline (19). Pivaloylation of the 2-amino group, followed by NBS bromination, condensation with di-tert-butyl N-(5-amino-2-thenoyl)-L-glutamate (28), and stepwise cleavage of the protecting groups with ammonia and TFA yielded. Treatment of 9 with acetic anhydride afforded 2,6-dimethyl-5-chlorobenz[1,3-d]oxazin-4-one (31), which on reaction with ammonia, NaOH was converted to 2,6-dimethyl-5-chloro-3,4-dihydroquinazolin-4-one (33). Bromination of, followed by condensation with and ester cleavage with TFA, yielded. The IC(50) of and against CCRF-CEM human leukemic lymphoblasts was 1.8+/-0.1 and 2.1+/-0.8 microM, respectively.     

Use of simplified substrates for the study of 5-lipoxygenase from RBL-1 cells

5,8,14-eicosatrienoic (5,8,14-ETA) and 5,8-eicosadienoic (5,8-EDA) acids are converted by the 5-lipoxygenase from RBL-1 cells into 5-hydroperoxy-6,8,14-eicosatrienoic (5-OOH-ETA) and 5-hydroperoxy-6,8-eicosadienoic (5-OOH-EDA) acids, respectively. These hydroperoxy fatty acids, unlike 5-hydroperoxy-6,8,11,14-eicosatetraenoic acid (5-HPETE), are not further processed into leukotrienes by the leukotriene A4 synthase activity of 5-lipoxygenase. 5,8,14-ETA was used to establish the saturation kinetics of 5-lipoxygenase in the 100,000g supernatant from RBL-1 cells. The study was performed by measuring the rate of product formation at optimal concentrations of the cofactors, calcium and ATP. Kinetics performed at various concentrations of supernatant did not follow the Michaelis-Menten equation. This aspect is discussed in relation to the presence of hydroperoxide-reducing system(s) in the supernatant. 5,8,14-ETA and 5,8-EDA turnover rates were also compared.     

Cytotoxic bromoindole derivatives and terpenes from the Philippine marine sponge Smenospongia sp

A detailed chemical analysis of a Philippine marine sponge Smenospongia sp. has been performed. This study yielded four new metabolites, 5-bromo-L-tryptophan (1), 5-bromoabrine (2), 5,6-dibromoabrine (3) and 5-bromoindole-3-acetic acid (4). The pyrroloiminoquinone alkaloid, makaluvamine O (5) as well as 5,6-dibromotryptamine (6), aureol (7) and furospinulosin 1 (8) were also isolated. Although 1 and 4 have been synthesized previously, this is the first report on the isolation of these compounds from a natural source. The furanosesterterpene furospinulosin 1 (8) was obtained for the first time from the genus Smenospongia. The structures of all compounds were established by spectroscopic methods (UV, IR, 1D and 2D NMR, MS, [alpha]D). The cytotoxic potential of 1-8 was evaluated in a panel of isogenic HCT-116 human colon tumor cell lines.     

The anti-cancer,anti-inflammatory and tuberculostatic activities of a series of 6,7-substituted-5,8-quinolinequinones

A variety of 6,7-substituted-5,8-quinolinequinones were synthesised and assessed for their anti-tumour and anti-inflammatory activities, and their ability to inhibit the growth of Mycobacterium bovis BCG. In particular, the introduction of a sulfur group at the 7-position of the quinolinequinone led to the discovery of two compounds, 6-methylamino-7-methylsulfanyl-5,8-quinolinequinone (10a) and 6-amino-7-methylsulfonyl-5,8-quinolinequinone (12), that exhibited selectivity for leukemic cells over T-cells, a highly desirable property for an anti-cancer drug. A number of anti-inflammatory (AI) compounds were also identified, with 6,7-bis-methylsulfanyl-5,8-quinolinequinone (18a) exhibiting the highest AI activity (0.11 μM), while 6,7-dichloro-5,8-quinolinequinone (7a), 6,7-dichloro-2-methyl-5,8-quinolinequinone (7b), and 6,7-bis-phenylsulfanyl-quinoline-5,8-diol (19) also exhibited good AI activity and specificity. Several quinolinequinone TB-drug candidates were identified. Of these, 6-amino-7-chloro-5,8-quinolinequinone (11) and 6-amino-7-methanesulfinyl-5,8-quinolinequinone (14), exhibited low MICs (1.56–3.13 μg/mL) for the 100% growth inhibition of M. Bovis BCG. Some general trends pertaining to the functional group substitution of the quinolinequinone core and biological activity were also identified.     

Synthesis and biological evaluation of quinoxaline-5,8-diones that inhibit vascular smooth muscle cell proliferation

A series of 6-arylamino-2,3-bis(pyridin-2-yl)-7-chloro-quinoxaline-5,8-diones were synthesized and evaluated for their inhibitory activity on the rat aortic smooth muscle cell (RAoSMC) proliferation. The quinoxaline-5,8-diones exhibited a potent antiproliferative activity. Further mechanistic study revealed that the inhibitory effect of one representative quinoxaline-5,8-dione on SMC proliferation was mediated by modulation of the extracellular signal-regulated kinase 1/2 signaling pathway in the RAoSMCs.     

Naphthazarin derivatives (II): formation of glutathione conjugate, inhibition of DNA topoisomerase-I and cytotoxicity.

6-(1-Hydroxyalkyl)-5,8-dimethoxy-1,4-naphthoquinones, expressing a higher reactivity in conjugation with glutathione, showed a greater potency in the inhibition of DNA topoisomerase-I and the cytotoxicity against L1210 cells than 2-(1-hydroxyalkyl)-DMNQ derivatives, implying the participation of electrophilic arylation in the bioactivities. In further study 6-(1-Hydroxyalkyl)-5,8-dimethoxy-1,4-naphthoquinones with an alkyl group of shorter chain length (C2-C6) exerted a greater bioactivities than those with longer chain length(>C6).